FIG. 1 hereof, from Stouffer U.S. Pat. No. 4,151,955 (incorporated herein by reference), discloses a two-stage fluidic spray device in which a wall attachment, heavy-ended type of fluidic oscillator 10 drives a generally circular outlet region or chamber 11. Outlet region 11 has a substantially concentric island 12 which converts the fluidically swept jet issuing from fluidic oscillator to sweeping sheet. FIG. 2, from Stouffer U.S. Pat. No. 4,508,267 (incorporated herein by reference) discloses a liquid oscillator for producing a unidirectional swept jet for producing a fan spray 16 with resulting liquid droplets of uniform size. The oscillation chamber has sidewalls which are shaped to produce alternating control vortices in the oscillation chamber 17 and preclude the wall attachment effects which make the fluidic oscillator portion or spray shown in FIG. 1 heavy-ended.
We have discovered that a two-stage liquid spray device having an outlet region with an island of the type illustrated in Stouffer U.S. Pat. No. 4,151,955 and a fluidic oscillator of the type shown in Stouffer U.S. Pat. No. 4,508,267 can be operated at low pressure (as from a pumped source or a plastic squeeze container) to achieve full-area coverage with substantially uniform droplets and wherein all of the spray droplets land on the desired work surface and do not bounce. In other words, the liquid droplets stay on the work surface in the desired pattern.
The exit aperture from the outlet stage to ambient is provided with a transverse groove to define the extent of the oscillating liquid sheet forming the spray.
The object of the present invention is to provide a liquid spray device for full area coverage which operates at low pressure and velocity and which produces substantially uniform droplets in the full area coverage spray.
According to a preferred embodiment of the invention, a two-stage fluidic spray device in which a fluidic oscillator has an oscillation chamber with mirror image sidewalls shaped to produce alternate control vortices that cause the power jet to oscillate back and forth in the oscillation chamber without significant wall attachment effects. The output of the fluidic oscillator drives an island type output region. The exit aperture or opening from the outlet region to ambient is provided with an external transverse groove or slot which defines the lateral boundaries of the spray pattern of liquid and substantially eliminates any drip.